Exploring, drilling and completing hydrocarbon wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years increased attention has been paid to monitoring and maintaining the health of such wells. Significant premiums are placed on maximizing the total hydrocarbon recovery, recovery rate, and extending the overall life of the well as much as possible. Thus, logging applications for monitoring of well conditions play a significant role in the life of the well. Similarly, significant importance is placed on well intervention applications, such as follow on clean-out or isolation techniques which may be utilized to enhance hydrocarbon recovery over time.
In addition to monitoring and more directly interventional applications, the completions architecture of the well often includes sophisticated level of hardware incorporated into the well from the outset. For example, a steel casing may be utilized to help define the well and promote rapid uphole production of well fluids. Once more, chemical injection lines may run to predetermined downhole production locations such as at casing perforations, a screen or slotted pipe. Thus, a significant buildup of irregular occlusive scale, wax and other debris may be avoided, thereby further promoting the noted production.
Along the same lines, the architecture of the well may include zonal isolation hardware, production tubing, and/or control valve governance so as to enhance desired types of production from the surrounding formation or injection into it. For example, while certain types of hydrocarbon fluid recovery is generally desired, the possibility of one or more regions of the formation beginning to produce water may arise. Thus, the well may be constructed of architecture which allows for production from the water producing regions to be shut off in circumstances where this is prone to occur. As such, continued production of the desired hydrocarbons through production tubing and the main bore of the well may continue without interference of water production.
As indicated, flow control valves may be utilized in helping to govern production from various zones. More specifically, fluid flow through each zone may be reversibly regulated by such a valve. Thus, production may be closed off should water be produced. Additionally, closure may be more temporary, for example in conjunction with an intervention. Subsequently, the valve may be reopened where production timing and type so dictate.
A control valve as described above is often comprised of a sophisticated hydraulic control module that regulates the operation of a full size hydraulically operated completions tool, such as a flow control valve, a safety valve, formation isolation valve or the likes. While fairly small for sake of limited downhole space, shear valves are nevertheless particularly adept at handling high pressure differential exposure which is common in the downhole environment. For example, a shear valve may operate by way of separate lines routed through a central shear space of the valve. Nevertheless, in circumstances where one line is particularly high pressure, say in excess of about 5,000 PSI, and another line is of fairly negligible pressure, the valve may be well suited to switch between lines without malfunction for long periods of time. That is, in spite of sudden exposure to a dramatic spike or drop-off in pressure, the valve is architecturally configured to effectively function. This is namely due to the metal to metal sealing interface between the internal seal member of the shear valve and the adjacent housings of the noted lines.
While well suited for use in environments where such differentials are present, a shear valve may require several subcomponents to achieve the desired functionality. For example, where the shear valve is internally energized by an elastomer, the material is prone to swell and degrade over time. This is due to the high temperature downhole fluid environment of the well. Thus, as a practical matter, an elastomerically energized shear seal may be limited in reliability in the long run.
In order to address the life deficiency issues of an elastomeric-based shear valve, a spring-based energizer may alternatively be utilized. In a spring-based energizer, concerns over swelling and material degradation are largely removed. However, as noted above, the shear valve for downhole applications may need to be fairly small and of comparatively narrow tolerances. By way of example, to serve as a control valve in the well, a shear type valve which is internally spring-based may utilize a spring that is about ⅛ of an inch or less in diameter. Once more, as also noted above, this spring would be sandwiched between adjacent metal interfaces of similar sizing. As a result, the functionality of the valve would now be reliant on the consistency of precision in construction among three separate, very small metal pieces (i.e. a spring and two metal interfaces). As a practical matter, the reliability of the valve is left in the hands of an extremely small thin wire spring with dead end coils sandwiched between adjacent interfacing blocks of metal.
A spring-based energizing shear valve as described above is likely to outsurvive a comparable elastomeric-based version in a downhole environment. For example, it is not uncommon to see about a ten year survivability requirement from such shear valves. However, given the narrow tolerances and fragile nature of the spring, the manufacturing of such a valve in large quantities may get complicated and expensive. Therefore, operators are often left with the undesirable choice between tolerating a loss in long term reliability or accept excessive production cost due to low yields.